Mesoporous Methyl-Functionalized Titanosilicate Produced by Aerosol Process for the Catalytic Epoxidation of Olefins

• Published in: Catalysts Vol. 11; no. 2; p. 196
• Main Authors: Manangon-Perugachi, Lucia E., Smeets, Valentin, Vivian, Alvise, Kainthla, Itika, Eloy, Pierre, Aprile, Carmela, Debecker, Damien P., Gaigneaux, Eric M.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.02.2021
• Subjects: Adsorbed water; aerosol-assisted sol-gel; Aerosols; Alkenes; Atomic emission spectroscopy; Butyl hydroperoxide; Catalysts; Chemical reactions; Chemical synthesis; Dispersion; Emission analysis; Epoxidation; Hydrophilicity; Hydrophobicity; Inductively coupled plasma; mesoporous titanosilicate TiO2-SiO2; NMR; Nuclear magnetic resonance; olefin epoxidation; one-pot methyl-functionalization; Oxidizing agents; Silicon dioxide; Sol-gel processes; surface hydrophobicity
• ISSN: 2073-4344; 2073-4344
• DOI: 10.3390/catal11020196

Titanosilicates (Ti-SiO2) are well-known catalysts for the epoxidation of olefins. Isolated Ti inserted in the silica framework in tetrahedral coordination are the active species. Recently, adjusting the hydrophobic/hydrophilic balance of such catalysts’ surfaces has appeared as a promising tool to further boost their performance. However, adjusting the hydrophobic/hydrophilic balance via a one-pot classical sol-gel generally leads to a decrease in the Ti dispersion and/or collapse of the pore network. To overcome this limitation, hydrophobic mesoporous Ti-SiO2 were here synthesized by aerosol-assisted one-pot sol–gel, which allowed the simultaneous control of their Ti loading, degree of methyl-functionalization, and textural properties. Methyl-functionalization was achieved by a partial substitution of tetraethoxy silane (TEOS) by methyltriethoxy silane (MTES) in different ratios. Solid-state 29Si-NMR, FTIR, TGA, and vapor-phase water adsorption showed that methyl moieties were effectively incorporated, conferring a hydrophobic property to the Ti-SiO2 catalysts. ICP-AES, DRUV, XPS, and N2 physisorption demonstrated that Ti dispersion and textural properties were both successfully preserved upon the incorporation of the methyl moieties. In the epoxidation of cyclooctene with tert-butyl hydroperoxide as oxidant, the hydrophobic Ti-SiO2 showed higher catalytic performance than pristine Ti-SiO2 prepared without MTES. In addition to disentangling the positive effect of adjusting the hydrophobic/hydrophilic balance of epoxidation catalysts on their performance, this contribution highlights the advantages of the aerosol procedure to synthesize mesoporous functionalized catalysts with very high dispersion of active sites.